Method for roll forming and machine and blank for this

ABSTRACT

Method for the fabrication of cones of sheet material where the blank includes two curved edges that are circular and have the radius R and r respectively and a common center C. The blank further has two straight lateral edges which are angled in relation to the circular edges. An angle α between the radius, through a corner and a first straight edge is as great as an angle β between the radius through a second straight edge. A frustum of a cone is obtained from the blank after rolling the cone such that the lateral edges have been united to make a joint that runs helically around the cone.

This invention concerns a method and a machine for the fabrication of aconical mantle of sheet material, in particular a frustrum of a coneintended to be press rolled further to final shape. The invention alsoconcerns the starting blank of the cone. According to the invention madecones may with advantage be used at the fabrication of water cyclonesintended for the cleaning of waste water as well as fibre suspensions inpaper mills.

According to previously known technique fabrication of conical mantlesmade from sheet material starts with the milling of ring shaped sheetsegments so that they take conical shape. Examples of this are describedin the U.S. Pat. Nos. 3,016,082, 3,091,279, 3,287,953, 3,623,349,4,195,509 and 4,735,076. At the rolling according to the known techniquethree or four rollers are used and the sheet blank is subjected to moreforceful deformation in its more narrow, the upper end of the conecorresponding end and its rolled so that the opposing radial sides ofthe ring segment meet, whereafter these are joined together.

It is also known to fabricate cones by in a number of operationspressing a blank so that it finally receives a conical shap. Sincehowever this method includes many steps it is practically impossible toguarantee an entirely round shape. At the use of cones made in this wayfor the fabrication of for instance cones in cyclones by subsequentpress rolling a part of this unroundness will remain. In particular theunroundness that is a result of the weld often remain.

It has in reality turned out to be difficult or perhaps even impossibleto secure that the cross section of the cone becomes round. Generallythe radius in the area close to the edges that are to be joined becomesomewhat longer than intended, i.e. it is difficult to make the curvingto continue all the way to the edge. Furthermore the forces necessaryfor the shaping closest to the edge increase to very high values. Inreality thus the edges that are to be joined will remain entirely flat.This phenomenon results in turn in that a corner is accrued in the cone.If the cone is to be used at the fabrication of a cyclone, vortexcleaner or the like such a corner noticeable diminish the separatingability of the cleaner by turbulence being generated at the corner orcorners. Furthermore an unround cone is worn faster in a cyclone. If oneattempts to apply larger forces in order to achieve a counteracting ofthis tendency there is a risk that an indentation take place instead.This also result in turbulence and unsatisfactory separation and greatwear. Also when a cone made in this way is machined additionally by forinstance press rolling normally the tendency for unroundness remain inthe final product.

The risk for unroundness in the final product is not only a result ofthe rolling itself but may also be result of welding. The welding heatnamely result in a tendency to bend the sheet material in the edge area.Since a weld furthermore always has a tendency to shorten somewhat whenit has cooled off one risks not only to obtain unroundness but also abending of the cone in its length direction.

Of the above mentioned methods for the fabrication of cones the rollingmethod has the drawback that the blank will be too flat close to thejoint to give a good roundness at the welding while the successivepressing in tools although giving greater possibility to counteractthis, simultaneously easily result in a great number of corners for thecone corresponding to the joints between the different bending steps.The latter method also has the drawback with great tooling costs andmany steps in the work. The known method result in circumstantialfabrication, large cassation risk and an expensive final product.

At the shaping the blank often passes through two or more bending orrolling phases. In the first the sheet is bent to a certain extent sothat the final product from the second phase will be as close aspossible to the conical shape. The cone is then removed from the bendingstation and transferred to a joining station in the shape of a weldingautomat. In particular at fabrication through bending in tools thenumber of work steps may be considerable.

In view of the above problems the invention has as its object to definea fabrication method, a machine and a blank for the making of cones, andthen in particular frustrums of cones that can than be used as astarting blanks at pressure rolling to final shape. This object is inaccordance with inventions solved by the joint (weld) that joins theedges of the sheet blank to each other being arranged helically aroundthe cone. This gives however a long joint and thereby weld and therebyseemingly an increased risk of unroundness for the final cone. Howeverin reality a considerably far better roundness is achieved than at theknown methods. This depends on the required shaping not taking place inparallel with the edges of the joint as in the known method but at angleto the this. As a result of this the bending of the blank to its conicalshape will continue all the way out to the edges when joining is to takeplace. In addition to resulting in an improved roundness at the jointafter the welding this also result in smaller shaping forces than at theknown methods and furthermore the shaping forces are more uniform duringthe entire shaping.

The blank is at rolling in accordance with the invention controlled sothat it turns around tip of the cone in order to place lateral, forjoining intended edges correctly next to each other. The gripping andcontrol of the blank in relation to shaping tools can preferably takeplace by the blank being gripped and or controlled so that the circularpart of the blank that is to constitute the base edge of the conefollows a circle path, the radius of which equals the radius of thecorresponding part circle edge of the blank and that the samerelationship applies for the other circle segment shaped edge. Possiblythe shaped base edge may be guided along a circle corresponding to thebase edge of the cone, while for the part of the blank that has not yetbeen shaped the blank is guided so that its the upper edge of the coneconstituting circle segment follows a circle with a correspondingdiameter, preferably in a plane tangential to the cone to be.

An additional advantage with the invented fabrication method is that thewelding together of the blank to a cone partly can take placesimultaneously with the shaping. As soon as two edges of the blanks hascome to lie close to each other the welding together of the jointestablished in this way can start simultaneously as the remaining partof the cone is shaped. The welding is then ended somewhat after theending of the shaping itself. It is in other words possible to make aready cone directly from the starting blank without the cone having tobe transferred between different machines and work stations. This meansa saving in time and money.

In order to enable welding simultaneously with the shaping of the blankto a cone the blank may not be held too close to the joint itself butthis is preferably done a short distance from this during shaping.Possibly a blank can be provided with projecting tabs that later can becut away.

When the rolling method according to the invention is used to makeblanks that are then to be roll shaped to their final shape it is usualto weld a disc to the narrow end of the conical blank so that the blankcan be held with this disc that is clamped axially. In accordance with afurther development of the inventive thought one may however considermaking the conical blank somewhat longer in its narrow end and that thisend at the mounting before the pressure rolling is deformed betweenoppositely situated coglike or toothed elements so that a crown-likeshape is obtained, achieving an axial holding of the blanc as well as agood torque transfer.

By choosing the rolling direction at a subsequent pressure rolling onthe blank the rolling can take place against or in the direction of thehelix. Since the joint helix possibly has a different composition or atleast when worked can behave somewhat different than the remainingmaterial there is the risk that the joint in particular becomes to shortand consequently tries to follow a smaller diameter all the way than theremaining ready cone. This can be counteracted by an opposed pressurerolling against the helix, that is the cone turns during working in adirection corresponding to a shortening of the joint so that thetendency of the joint to become to short is counteracted. Possibly theroundness may be controlled more accurately by effecting rolling inalternating directions until desired roundness is achieved, possibly acontinuous monitoring with repeated alternating of the rotationaldirection can take place to secure that the desired roundness during theentire working time is maintained and in particular is present at thesame time as a cone is through with the pressure rolling.

In order to make it possible for the welding to take place in anentirely horizontal joint also the entire machine used or only itsrolling parts may be turnable or tilltable in order for an adaption todifferent cone angles.

The method, the machine and the blanks in accordance with the inventionprovides a rapid fabrication of ready cones as well as conical blanksfor continued working with exactness and a low tooling cost. Forinstance the machine may include a shaping mandrel on which the blank isrolled up. At this only one corresponding shaping mandrel must be madefor each cone angle. Since the shaping mandrel may be fabricated byturning the price will furthermore be comparatively reasonable, this inparticular in relation to the method with pressing the blank to itsfinal shape in a number of steps and with dollies and dies.

Even if one as filler material for the weld joint uses thread or stripsmade from the same sheet metal as the blank one must calculate with thehigh temperature at the welding resulting in a variation in the materialcomposition that in turn result in a somewhat differing behavior at thesubsequent rolling.

Further advantages and characteristics of the invention are apparentfrom the patent claims and from the following description of preferredembodiments of invention, shown in the drawings. In the drawings FIG. 1shows a blank according to previously known technique, FIG. 2 acorresponding cone, FIG. 3 a blank according to the first preferredembodiment of the invention, FIG. 4 shows a cone made from the blank inFIG. 3, FIG. 5 shows a second preferred blank in accordance with theinvention, FIG. 6 a cone made of the blank in FIG. 5, FIG. 7 shows amachine for the execution of the method in accordance with theinvention, FIG. 8 shows a detail the machine in FIG. 7 and FIG. 9 a coneblank.

In FIG. 1 is shown a flat sheet blank 2 made by two circular edges 4 and6 with a common center C. The blank 2 constituting a segment has alsotwo apposed straight radially running side edges 8 and 10 the extensionsof which intersect in the center C of the circle. In FIG. 2 is shown howthe blank 2 in FIG. 1 has been rolled to a frustrum of a cone so thatthe lateral edges 8 and 9 of the blank lies neighboring to each otherand have been joined together there.

FIG. 3 shows a blank in accordance with a first preferred embodiment ofthe invention. The blank 22 includes two curved edges 24 and 26 that arecircular and have the radiuses R and r respectively and a common centerC. The blank furthermore has two straight lateral edges 28 and 30, whichinstead of being arranged radially are arranged angled in relation tothe radial direction. An angle a between the radius through the corner Aand the edge 30 and an angle β between the radius through the comer Band the edge 28, which angles are equal.

In FIG. 4 the frustrum of a cone is shown that is obtained from theblank in FIG. 3 after the rolling of this to a cone were the lateraledges 28 and 30 has been joined to make a joint 32 that runs helicallyaround the cone.

In FIG. 5 is shown an alternative embodiment of blank in accordance withthe invention. Also this blank is constituted by two curved edges 124and 126 that are parts of separate circles and the lateral edges 128 and130. In relation to the previously shown embodiment the lateral edges128 and 130 are arranged tangential in relation to the inner edge 126.In FIG. 6 is then shown how the lateral edges 128 and 130 joinedtogether to a joint 132 encloses an angle γ with a plane perpendicularto the axis of the cone at the wider end of the cone and how this angleis reduced towards the thinner end of the cone.

In order to secure that the circles that constitutes the upper and lowerends of the frustrum of a cone are perpendicular to the axis of the conethe curved edges of the blank must constitute parts of circles with acommon center for the curvature. At the rolling it is preferable thatthe rolling axis goes through this center. Furthermore the lateral edgesmust have the same length and shape if a cone with straight sides are tobe achieved. The lateral edges need not necessarily to be straight butmay also be curved or shaped in some other way to grip into each other,but to establish a good joint they must have a coinciding shape. FIG. 9can be said to show a blank that has been bent back to flat conditionafter the drawing of a number of generatrixes in the cone. As isapparent the lines are perpendicular relative the curved edge 224 aswell as the curved edge 226, that is the ends of the cone.

The above described blanks are not practical to use for the fabricationof cones that become more and more pointed or even include their actualtip, since the blank would become very thin close to the tip and thewelding length would become very large close to this. If therefor apointed cone is desired one can consider the joint to be arranged withhelical shape to a certain level in the cone whereafter it runsessentially along a generatrix. The transit may course be smooth.

The arrangement of a fixation tab extending downwards of the cone itselfalso has the advantage that the corner first rolled of the cone can beshaped all the way from the tip. This has in dashed lines been shown inFIG. 5 and been denoted 136, in the same figure it has also been shownin dashed lines how the cone may be extended upwards with one or severaltabs 137 to establish the fixation at the following pressure rolling.

Since it may be difficult satisfactory to join together the outermosttip of the blank with the remaining already fabricated part of the coneit may even from this reason be advantageous to allow the blank in thisarea to be somewhat too large, which part then at a suitable opportunitycan be cut away when the cone is ready or before this be used for theholding at the pressure rolling.

The above described blanks may be shaped in different ways to theirconical form but preferably this takes place in a rolling or millingprocess enabling an entirely continuous shaping in one step to finalform. Due to the helical shape the bending that is required will becomparably moderate and the bending may therefor take place to fmaldimensions in one step. The shaping may be achieve by means of threerolls in a known manner or by rolling the blank on a core or mandrel.

The machine shown in FIG. 7 for cone fabrication includes a shapingmandrel constituted by a lining 60 arranged on an axle 58. The axle 58is journaled in two roll bearings 54 and 56 and can be turned around bya two pinions 62, 64 and transmission 50 driving the latter of thesepinions connected to a not shown power source. When cones with an otherangle or other diameters are fabricated the lining may be exchangedalternatively one can consider to exchange the entire shaping mandrelincluding lining as well as axle and pinion 62 and possibly also thebearings.

The shaping mandrel 60 is at its base end provided with a bridge likepart that has been denoted 70, in which a lip extends out over theconical surface of the mandrel and in this lip is a threaded a bolt thatis intended for the holding of the blank 72. Parallel to the rotationalaxis of the shaping mandrel a beam 52 is arranged shortly below theshaping mandrel. On this beam 52 is fastened a console 66 that via aball joint 67 carries an arm 68. The arm 68 is in its outer end providedwith a fork like part were a bolt 74 is threaded for the clamping of theblank 72. A console 66 is displaceably and fixably arranged on the beam52 to enable adjustment so that it is placed exactly in the center ofthe theoretical extension of the generatrixes of the shaping mandrel.

On a lower down in the machine in a frame arranged additional beam 44,that runs entirely parallel to the axis of the shaping mandrel, an armis arranged displaceable and pivotably supporting the pressure roll 80shown in FIG. 2. The arm is preferably displaceable lengthwise of themachine and adjustable to its turning angle so that the pressure rollcan be placed parallel with the side of the shaping mandrel and canfurther more be swung or displaced latterly in accordance with thethickness of the sheet from which the cone is to be made. The pressureroll is divided into a number of short rolls or rings arranged close toeach other and relative each other freely tumable for adaption to theperipheral speed of the shaping mandrel and blank, which peripheralspeed varies over the length due to the diameter variation.

At the fabrication of a sheet material cone, for instance for thefabrication of a blank that is then to be rolled to its final shapes,the blank 72 is fastened to the shaping roll 60 by the lip 70 beingswung down to lie entirely horizontally in relation to the axis of themandrel. The blank 72 is placed parallel to the lateral surface of themandrel so that the blank principally lies tangentially in relation tothe mandrel. The blank is clamped a distance from the corner, this inorder to make it possible for the not shown welding device to weld thejoint all the way from the base of the cone. Furthermore the fork likeend of the arm 68 is with the bolt 74 fastened in the blank in thecurved portion of the blank that is to constitute the thinner end of thecone. The blank 72 extends up between the shaping mandrel 60 and thepressure roll 80 (FIG. 8). The mandrel is now brought to turn and atthis pulls the blank 72 upwards. The pressure roll presses the blankagainst the mandrel and the blank is shaped after the mandrel. Since theshaping starts in the wider end of the mandrel the initial deformationwill not be so forceful, instead the necessary forces that are requiredwill be comparably moderate, in particular in comparison with conventualshaping. As the mandrel successively rolls up more and more of the blankthis moves upwards during a simultaneous turning of the arm 68 aroundits journaling point in the console 66. In this way the blank ispositively controlled by the fastening 70 on the mandrel and fastening74 at the arm. At none of these places any relative movement have totake place since the fastening is arranged in relation to the blank inthe same manor at it also will be located when the shaping is ended.When the mandrel has rotated an entire revolution the entire base edgeof the cone has been achieved and the lowermost edge of the blank 72 isplaced close to the first running on and uppermost edge. When then thejoint after an additional quarter of a revolution reaches the uppermostposition during the rotation of the mandrel the welding of the joint iscommenced by a not shown automatic welding device. During the continuedturning of the mandrel and thereby continued establishing of the jointalso the welding continues, still exactly above the axis of the mandrelin the length direction of this. The control of the welding can beelectronic, optical, mechanical or combinations thereof.

In order to secure optimal welding conditions the machine is preferablytiltable, for instance turnable around the axis 73 in order to securethat welding always takes place in an entirely horizontal joint. If onewould wish to move the location of the welding closer to the pressroller one can consider a turning up of this or a higher placing, whichmay be achieved by turning the machine around a longitudinal axis thatmay for instance be constituted by the beam 52.

The arm 68 can either be made free from the blank 72 when the weldingoperation has been started and thereby the cone in making and the blankcan not move not any more even if freed from the arm. Alternatively thearm can remain during the entire operation if the cone is longer thanthe shaping mandrel or if at the shaping mandrel is arranged acorresponding recess for the end of the arm.

The fastening means 70 and 74 for the holding of the blank may also beconstituted by manually, hydraulically, pneumatically, or electricallyactivated quick coupling means.

In order to supply protective gas as well as to prevent too much coolingfrom below of the weld a helical recess may be arranged corresponding tothe helix of the joint in the mantle surface of the shaping mandrel. Thearm 68 is adjustable to its length for adaption to the amount of theintended cone that is to be cut away at the fabrication of the intendedfrustrum of a cone as well as to the making of different cones.

The above described fabrication method with an arm as the guide may alsobe used at a rolling method with three rolls. In order here to securethat the lower edge of the cone the entire time is held in the correctposition one may either arrange a corresponding turnable guiding thatrotates around the theoretical axle of symmetry of the cone and to whichthe blank of the cone is fastened with the first rolled corner.

Instead of controlling the blank during its rolling up on a mandrel bymeans of the above described arm one can consider that the blank withits outer circular edge that is to constitute the base edge of the coneis allowed to lie against a radial flange on the mandrel. The flange maypossibly be provided with a circular groove into which the base edge ofthe cone during the shaping successively is swung into. Since the blankis drawn past the press roll achieving the deformation there will allthe time exist a force that holds the blank pressed against the radialflange.

Instead of holding the blank in the base part of cone with a clampingbolt one can consider a pin gripping into a hole in the blank or thatthe blank is extended with a hook like part that its hooked over a pinor the like.

What is claimed is:
 1. Method for the fabrication of a cone or a part thereof by rolling and welding of sheet material, in particular frustum of a cone, in particular intended as a starting blank at press rolling of cones intended for cyclones, characterized in that the joint is arranged helically.
 2. Method according to claim 1, characterized in that the blank at the shaping to a cone is positively guided at at least two fixations points, in such a way that the movement center of the blank during the shaping is positively controlled to coincide with the tip of the cone.
 3. Method according to claim 2 for the fabrication of frustum of cones, characterized in that the lower base edge of the cone is positively guided to the circle that it is to constitute.
 4. Method according to claim 1, characterized in that the joint is welded simultaneously with continued rolling of the blank.
 5. Method according to claim 1, characterized in that the fabrication of the cone is ended with a press rolling of this between a mandrel and a press roller, the turning direction being so arranged that the turning angle of the helical joint at the plastic deformation tends to diminish.
 6. Machine for the execution of the method in accordance with claim 1, characterized in that it includes a conical shaping roller, a press roller that can be pressed against this, and a fastening means for holding of the blank at the holding mandrel, in particular its first rolled on corner.
 7. Machine according to claim 6, characterized in that it includes an arm journaled pivotable in the tip of the mandrel respectively the tip of the cone in a plane that is tangent plane to the cone and that the arm in the other end is fastened to the blank and that the sum of the length of the arm and the length from the base edge of the blank to the fastening point and the arm in this along a generatrix of the final cone equals the length of a generatrix in the intended cone.
 8. Machine according to claim 6, characterized in that the shaping roller is provided with a helical groove over which the welding of the joint is to take place.
 9. Machine according to claim 6, characterized in that the machine is tiltable so that the weld may be arranged horizontally even at different cone angles.
 10. Machine according to claim 6, characterized in that the shaping mandrel is exchangeable and that the turning center of the arm is displaceable along the center line of the cone for adaption to different cone sizes and cone angles.
 11. Blank for the fabrication of frustum of cones of sheet material with helical joint, characterized in that it includes a first part of a circle with a large diameter and a length corresponding to the largest diameter of the frustum of a cone and a second border line that also constitutes a part of a circle intended to constitute the end of the cone with the smaller diameter, which circles have the same center and at which the length of the generatrix of the frustum of a cone equals the diameter difference between the two circles and that the blank is further limited by two edges each extending between the other ends of the circle parts and at which the angles between these side edges and the circle parts differs from 90°.
 12. Blank according to claim 11, characterized in that the edges extending between the circle parts have the same shape and length. 